JP4761973B2 - Radio control apparatus and transmission power control method - Google Patents

Description

  The present invention relates to a radio network controller and a transmission power control method.

  In a CDMA mobile communication system, by performing transmission power control with high accuracy, it is possible to increase the capacity of a radio system by suppressing interference given to other users as much as possible while maintaining communication quality at a required level. In a CDMA mobile communication system, in order to make a received SIR (Signal to Interference power Ratio) close to a target SIR, a radio base station measures the received SIR, compares it with the target SIR, and transmits transmission power. The inner loop transmission power control that transmits and indicates to the mobile station as transmission power control bits, and the radio control device positioned above the radio base station receives the reception quality (for example, block error and block error rate). And has a two-stage configuration of outer loop transmission power control that instructs the radio base station about the target SIR in the radio base station so as to satisfy the target quality (see, for example, Non-Patent Document 1).

  The outer loop transmission power control is ideally performed every 1 [TTI]. For example, a block error is detected by CRC, and the target SIR is updated every 1 [TTI] as follows (see, for example, Non-Patent Document 2).

IF CRC check OK
Step_down = BLER_target * Step_size
Sir_target (n) = SIR_target (n-1) -Step_down
ELSE
Step_up = Step_size-BLER_target * Step_size
SIR_target (n) = SIR_target (n-1) + Step_up
"W-CDMA mobile communication system", supervised by Keiji Tachikawa, Maruzen “W-CDMA for UMTS”, Holma and Toskala, Jon Wiley & Sons, Ltd

  However, if the target SIR is changed for each TTI (Transport Time Interval), the control load of the wireless control device increases. Also, a large amount of the interface band between the radio network controller and the radio base station is consumed.

  Therefore, instead of changing the target SIR for each TTI, there is also known a method in which a certain time interval is provided, and the target SIR is calculated for each time interval by the algorithm shown above and notified to the radio base station. Yes.

  However, when this method is used, the quality remains degraded during the aforementioned time interval due to the difference between the target quality and the set target SIR. What is remarkable is that the communication quality required by BLER (Block Error Rate) and the target SIR to be set may change significantly when the line environment changes before and after performing SHO (Soft HandOver). is there. At this time, since the target SIR does not change in the time interval, there is a problem that the communication quality is greatly deteriorated.

  Therefore, in view of the above problems, the present invention provides a wireless communication device that reduces the control load of the wireless control device and the bandwidth load between the wireless control device and the wireless base station while preventing deterioration in wireless quality when the line environment changes. It is an object to provide a control device and a transmission power control method.

  In order to achieve the above object, the first feature of the present invention is that inner loop transmission power control is adopted between the mobile station and the radio base station, and outer loop transmission power control is adopted between the radio base station and the radio control device. A wireless base station that instructs the mobile station to increase or decrease the transmission power by comparing the target SIR notified from the radio controller and the received SIR of the signal received from the mobile station. A radio control apparatus for controlling, (a) a measurement unit that receives a data block from a radio base station and measures reception quality, and (b) calculates a target SIR based on the reception quality measured by the measurement unit (C) a first time from when the reception quality is measured to when the target SIR is notified to the radio base station after the reception quality is measured. The gist of the present invention is that the section is set to be shorter than the second time section from when the reception quality is measured until the target SIR is notified to the radio base station when the reception quality does not decrease. .

  According to the radio control device according to the first feature, the radio control device and the load on the band between the radio control device and the radio base station can be reduced while preventing deterioration of radio quality when the line environment changes. Can do.

  According to the radio control apparatus according to the first feature, the measurement unit detects a block error from the received data block, and the target SIR calculation unit calculates a target SIR based on the detected block error rate. When a block error is detected, the first time interval from when the error is detected until the target SIR is notified to the radio base station is detected. When no block error is detected, the radio base station It is preferable to set it shorter than the second time interval until the target SIR is notified to the station.

  According to this wireless control device, it is possible to detect deterioration of wireless quality with higher accuracy.

The target SIR calculation unit calculates a target SIR that increases by a predetermined ΔUP when an error is detected. If no error is detected for a predetermined time N _CNT [TTI], the target SIR calculation unit calculates BLER_target. As the error rate, it is preferable to calculate the target SIR that decreases by ΔDOWN by the equation (1).

  The second feature of the present invention is that inner loop transmission power control is adopted between the mobile station and the radio base station, and outer loop transmission power control is adopted between the radio base station and the radio control device. By comparing the radio control apparatus that calculates the target SIR based on the uplink channel quality received from the station, the target SIR notified from the radio control apparatus and the reception SIR of the signal received from the mobile station, A transmission power control method in a communication system comprising a radio base station that instructs a mobile station to increase or decrease power, comprising: (a) receiving a data block from a radio base station and measuring reception quality; (B) calculating the target SIR based on the measured reception quality; and (c) if the reception quality is reduced and the reception quality is measured. From the first time interval until the target SIR is notified to the base station, when the reception quality does not decrease, from the second time interval until the target SIR is notified after the reception quality is measured. And a transmission power control method including a step of setting a short time.

  According to the transmission power control method according to the second feature, the control load of the radio control device and the bandwidth load between the radio control device and the radio base station are reduced while preventing deterioration of radio quality when the line environment changes. be able to.

  According to the present invention, a radio control apparatus and a transmission power control method for reducing a control load of a radio control apparatus and a band load between the radio control apparatus and a radio base station while preventing deterioration of radio quality when a line environment changes. Can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic.

(Configuration of communication system)
As shown in FIG. 1, the communication system according to the present embodiment includes a base station 20 that is wirelessly connected to a plurality of mobile stations 10 a, 10 b, and 10 c, and a wireless control device 30 that manages the base station 20. Has been. In the present embodiment, the number of mobile stations that perform radio communication with the base station is “3”, but may be a number other than “3”.

  In the communication system according to the present embodiment, inner loop transmission power control is adopted between the mobile stations 10a, 10b, and 10c and the base station 20, and outer loop transmission power control is performed between the base station 20 and the radio control device 30. Is adopted.

  FIG. 2 shows extracted functions of the base station 20 and the radio network controller 30 according to this embodiment related to uplink transmission power control.

  The base station 20 includes a signal reception unit 21, a RAKE reception unit 22, an error correction decoding unit 23, a reception SIR calculation unit 24, a target SIR storage unit 25, a reception SIR comparison unit 26, and a TPC command transmission unit 27. With.

  The signal receiving unit 21 converts a signal received from the antenna from a radio signal to a baseband signal, and transmits the converted signal to the RAKE receiving unit 22.

  The RAKE receiving unit 22 performs despreading and maximum ratio combining using a pilot signal to extract a desired user signal.

  The reception SIR calculation unit 24 calculates the reception SIR using the signal of the pilot portion of the signal of the desired user.

  The reception SIR comparison unit 26 compares the target SIR stored in the target SIR storage unit 25 and notified from the radio network controller 30 with the reception SIR. As a result of comparison, if reception SIR> target SIR, a “Down” command is generated, and if reception SIR <target SIR, an “UP” command is generated and transferred to the TPC command transmission unit 27.

  The TPC command transmitter 27 transmits a “Down” command or an “UP” command to the mobile station.

  On the other hand, the signal subjected to RAKE reception is input to the error correction decoding unit 23. The error correction decoding unit 23 performs error correction decoding. The signal after error correction decoding is transmitted to the radio network controller 30.

  As shown in FIG. 2, the radio network controller 30 includes a block error detection unit 31 and a target SIR calculation unit 32.

  The block error detection unit 31 (measurement unit) receives a data block from the base station 20 and measures reception quality. For example, the block error detection unit 31 performs block error detection using a CRC (Cyclic Redundancy Check).

  The target SIR calculation unit 32 calculates the target SIR based on the reception quality measured by the block error detection unit 31 (measurement unit). For example, the target SIR calculation unit 32 calculates the target SIR based on the block error detected by the block error detection unit 31.

  Further, the target SIR calculation unit 32, when the reception quality is lowered, the first time interval from the measurement of the reception quality to the notification of the target SIR to the base station 20 when the reception quality is not lowered. Then, it is set shorter than the second time interval from when the reception quality is measured until the target SIR is notified to the base station 20. For example, when a block error is detected, the target SIR calculation unit 32 determines the first time interval from when the error is detected until the target SIR is notified to the base station 20 when no block error is detected. It is set shorter than the second time interval from when the detection is performed until the target SIR is notified to the base station 20.

  Further, when an error is detected, the target SIR calculation unit 32 increases the target SIR by a predetermined step: ΔUP, and immediately notifies the base station 20 of the target SIR that has been increased.

On the other hand, if no error is detected, it waits for a predetermined time N _CNT [TTI], and if no error is detected for N _CNT [TTI], it is reduced by ΔDOWN by equation (1). Calculate the target SIR.

  Then, the target SIR calculation unit 32 notifies the base station 20 of the decreased target SIR.

(Transmission power control method)
Next, the transmission power control method according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart showing an operation related to the outer loop of the wireless control device 30 in the present embodiment. Here, a case where the target SIR is calculated based on error detection using a block error rate as the reception quality will be described.

  Here, t1 and t2 are a timer for determining the presence or absence of a CRC error, and a timer for determining the timing for notifying the base station of the target SIR lowered by ΔDOWN when no CRC error is detected. Starts with t1 = 0 and t2 = 0.

  The time intervals T1 and T2 are determined by the system as a cycle for determining a CRC error and a cycle for sending a “Down” command, respectively. T1 may determine the presence or absence of a CRC error for each frame as TTI, or may reduce the load as a number · [TTI]. Also for T2, it is possible to increase the accuracy of transmission power control by frequently performing “Down” as a number · [TTI], or rarely perform “Down” as a few hundred · [TTI]. Thus, the load on the RNC can be suppressed as much as possible.

  In FIG. 3, first, the radio network controller 30 counts up the timer (t1) until t1 reaches T1 (S11), and when t1 reaches T1 (S10), performs a CRC error detection ( S12).

  When an error is detected (S13), the wireless control device 30 increases the target SIR by a predetermined step ΔUP (S14). Then, the raised target SIR is notified to the base station 20 (S20), and the process returns to the first process.

  On the other hand, when no CRC error is detected (S13), the wireless control device 30 resets the timer (t1) (S15). Then, when t2 has not reached T2 (S16), the wireless control device 30 counts up the timer (t2) (S17) and returns to the first process.

  On the other hand, when t2 reaches T2 (S16), the wireless control device 30 decreases the target SIR by ΔDown (S18), and resets the timer (t2) (S19). Then, the lowered target SIR is notified to the base station 20 (S20), and the process returns to the first process.

(Function and effect)
According to the radio control apparatus 30 and the transmission power control method according to the present embodiment, when the reception quality decreases, the first time interval from when the reception quality is measured until the target SIR is notified to the radio base station is determined. When the reception quality does not deteriorate, the reception quality can be set shorter than the second time interval from when the reception quality is measured until the target SIR is notified to the radio base station. That is, when the reception quality decreases and the target SIR needs to be raised, the target SIR is notified as soon as possible, and when the target SIR needs to be lowered, the target SIR is notified after a certain amount of time. As a result, it is possible to reduce the control load on the radio network controller 30 and the load on the band between the radio network controller 30 and the base station 20 while preventing deterioration in radio quality when the line environment changes.

  Further, in this embodiment, when a block error rate is used as the communication quality and a block error is detected, the first time interval from when the error is detected until the target SIR is notified to the radio base station is determined as a block error. Can be set shorter than the second time interval from when error detection is performed until the target SIR is notified to the radio base station. Thus, by calculating the target SIR using the block error rate, it is possible to detect the deterioration of the radio quality with higher accuracy.

If an error is detected, a target SIR that increases by a predetermined ΔUP is calculated. If an error is not detected for a predetermined time N _CNT [TTI], ΔDOWN minutes are calculated according to the above equation (1). It is preferable to calculate a target SIR that decreases.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, although the block error detection unit 31 has been described as detecting a block error in order to measure reception quality, a bit error or the like may be detected in addition to the block error. In this case, the target SIR calculation unit 32 calculates the target SIR based on the detected bit error rate or the like.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a configuration block diagram of a communication system according to the present embodiment. It is a block diagram of the configuration of a radio network controller and a base station according to the present embodiment. It is a flowchart which shows the transmission power control method which concerns on this embodiment.

Explanation of symbols

10a, 10b, 10c ... mobile station 20 ... base station 21 ... signal receiving unit 22 ... RAKE receiving unit 23 ... correction decoding unit 24 ... calculation unit 25 ... target SIR storage unit 26 ... received SIR comparison unit 27 ... TPC command transmission unit 30 ... Radio control device 31 ... Block error detection unit 32 ... Target SIR calculation unit

Claims (3)

Inner loop transmission power control is adopted between the mobile station and the radio base station, and outer loop transmission power control is adopted between the radio base station and the radio control device, and the target SIR notified from the radio control device. A radio base station that controls a radio base station instructing the mobile station to increase or decrease transmission power by comparing a received SIR of a signal received from the mobile station,
A measurement unit that receives a data block from the radio base station and measures reception quality;
A target SIR calculation unit that calculates a target SIR based on the reception quality measured by the measurement unit;
The target SIR calculation unit
A first time interval after performing measurement of the reception quality if the reception quality is decreased to notify the target SIR to the radio base station, the measurement of the reception quality if the reception quality is not reduced Set to be shorter than the second time period from when the target SIR is notified to the radio base station,
If an error in the received data is detected, a target SIR that increases by a predetermined ΔUP is calculated. If no error is detected for a predetermined time N _CNT [TTI], BLER_target is set as a target block error rate. A wireless control device that calculates a target SIR that decreases by ΔDOWN by the equation (1) .

The measurement unit detects a block error from the received data block,
The target SIR calculation unit calculates a target SIR based on the detected block error rate. When the block error is detected, the target SIR calculation unit performs error detection and notifies the radio base station of the target SIR. The first time interval is set to be shorter than the second time interval from when error detection is performed until the target SIR is notified to the radio base station when the block error is not detected. The radio control apparatus according to claim 1. Inner loop transmission power control is adopted between the mobile station and the radio base station, and outer loop transmission power control is adopted between the radio base station and the radio control device. A radio control apparatus that calculates a target SIR based on channel quality, and an increase in transmission power by comparing the target SIR notified from the radio control apparatus with the reception SIR of a signal received from the mobile station, or A transmission power control method in a communication system comprising a radio base station for instructing the mobile station to decrease,
Receiving a data block from the radio base station and measuring reception quality;
Calculating a target SIR based on the measured received quality;
A first time interval after performing measurement of the reception quality if the reception quality is decreased to notify the target SIR to the radio base station, the measurement of the reception quality if the reception quality is not reduced And setting a shorter time period than a second time interval from when the target SIR is notified to the radio base station.
In the step of calculating the target SIR, if an error in the received data is detected, a target SIR that increases by a predetermined ΔUP is calculated, and if no error is detected for a predetermined time N _CNT [TTI] , BLER_target is a target block error rate, and a target SIR that is reduced by ΔDOWN is calculated according to Equation (1) .

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